In a railway vehicle, pressurized air from an air source is supplied via air piping to pneumatic brake devices, air springs, automatic flap opening and closing devices and other such equipment. Ball cocks (3-way cocks) are provided in the abovementioned air piping for the purpose of repair and maintenance. A ball cock of this type is described in, for example, the disclosure of Japanese Utility Model No. 6-23802. A ball cock of this type will be described with reference to FIGS. 7-10.
The main body of a ball cock consists of a first member and a second member, inside which an inner aperture is formed and which is detachably connected to the first member. A primary-side opening and a secondary-side opening, connected to respective air pipes (not shown), are formed in opposing locations in such first and second members, respectively.
An axial aperture which communicates with the inner aperture is formed in the upper portion of the second member, and an air exhaust aperture is formed in the lower portion of such first member. Valve seat carrier elements are installed via respective seal elements at the inner sides of the primary-side opening and the secondary-side opening of the first and second members, respectively. Valve seats, made of synthetic resin, are supported by valve seat carrier elements. Further, the valve seats support a ball-shaped valve body in the inner hole in a manner such that it can rotate about a vertical axis. A plate spring is provided between the first member and the valve seat carrier element, and it pushes the valve seat to the valve body side.
A valve shaft is connected to the upper portion of the valve body, and this valve shaft passes through the axial hole and is connected to a stopper plate and a handle at the top of the second member. As shown in FIG. 9, the stopper plate has two engagement projections separated by an angle of 90 degrees. At the top of the first member there is formed a stopper which can be engaged by one or the other of the engagement projections consequent to rotation of the valve shaft of such valve body.
In valve body there is opened a communication aperture which passes horizontally through its central portion, and a side aperture which passes obliquely from one side portion of the valve body to the bottom portion. The central axis of the side aperture lies in a plane which is perpendicular to the communication aperture. In the state shown in FIG. 7, the primary side-opening and the secondary-side opening are connected via the communication aperture, but when the valve body is turned approximately 90 degrees by means of handle, the pass-through state between the primary-side opening and the secondary-side opening is cut off, and the secondary-side opening and the air exhaust aperture are connected via the side aperture and the inner aperture, as shown in FIG. 10, and thus exhaust of air from the secondary-side opening can be effected.
However, air piping in which a ball cock, as described above, is provided under the floor of a vehicle. Various types of equipment, as well as a large number of air pipes, are also suspended below this floor. Therefore, since it is necessary to avoid interference with these items, sometimes a ball cock is mounted upside-down, in order that the air exhaust aperture is located at the upper surface in a vertical direction of the ball cock, or it is mounted so that the air exhaust aperture is positioned in a horizontal direction.
If the installation is such that the air exhaust aperture is positioned horizontally or at the top surface of the ball cock, there is a problem in that it is easy for rainwater, dirt or other foreign material to penetrate into the interior of the ball cock via the air exhaust aperture and so the valve seats, as well as other parts, are subject to damage by this rainwater, dirt or other foreign matter. When this happens leakage of pressurized air from ball cock can occur. Further, since the diameter of the side aperture for exhaust of air is usually a comparatively large diameter of approximately 5 millimeters, there is also the problem that when air is exhausted from the secondary-side opening and through the side aperture, the air exhaust speed becomes too great, and thus it becomes difficult to ascertain the switching pressure of a pressure switch which is mounted on the air piping. Therefore, it becomes difficult to regulate the air pressure in the air piping at the time of air exhaust.